Help with CO2Scape

Because a single value would be a claim the input data cannot support. The pH you enter sits in the exponent of the equation, so the reading tolerance of your test does not add a few percent to the result, it multiplies it.

A pH read to ±0.2, which is about what a color-comparison drop test achieves, turns into +58% / −37% on the computed concentration. Carbonate hardness enters linearly and adds its own tolerance on top. The range you see is that arithmetic carried through honestly.

If you want a narrower band, narrow the input that dominates it. Moving from a drop test to a freshly calibrated pH probe takes the pH tolerance from ±0.2 to ±0.05 and visibly tightens the interval, because the app applies the tolerance of the method you told it you used. The carbonate hardness term is always carried at the half-degree resolution of an ordinary drop titration; that one is not selectable.

No, that is the feature. The KH/pH method assumes the carbonate system alone governs your pH. Peat and botanical tannins, active plant substrates, and phosphate or borate based buffers each introduce a second acid and base system. When one of them is present, the measured pH no longer reports on dissolved gas, and in documented soil setups the equation runs high by a factor of 12 to 19. A fourth lock applies above pH 7.8, where carbonate ion starts contributing to alkalinity and the approximation fails from the other direction.

An answer that is wrong by an order of magnitude is worse than no answer, because you would act on it. So the app states which declared ingredient invalidated the model and offers two routes that do not depend on the carbonate assumption: the drop checker, read against a reference solution of known carbonate hardness, and the degassed-sample comparison.

1. Measure the pH of your tank water.
2. Drive the gas out of a sample of the same water: about two hours with an air stone, or about a day in an open glass left standing.
3. Measure the pH of the degassed sample at the same temperature.

The difference between the two readings gives you the ratio of dissolved carbon dioxide between tank and equilibrium: each pH unit of difference is a factor of ten. Because it compares the same water against itself, whatever else is buffering that water largely cancels out. In the app this is the pH drop method: you enter the two readings, pick which baseline you hold to be correct, and get the result with the same error band as everywhere else. The waiting happens in a glass, but the app runs it: pick the method, start the timer, and it tells you when the sample is ready. It also refuses a baseline that reads below the tank, and warns you when the two readings sit closer together than the pH method you selected can resolve.

Usually the checker, with a caveat. A checker filled with a reference solution of known carbonate hardness responds to dissolved gas only, and it is unaffected by the rest of your water chemistry. Its weakness is lag: it trails the tank by roughly one to two hours, so during a ramp-up it reads the past.

If the calculated range and the checker disagree persistently in a steady-state tank, treat that as a signal that one of your inputs is off, most often a carbonate hardness titration read one degree too high, or a pH probe that has drifted since its last calibration.

The actual water temperature at the moment of the pH reading, not the thermostat setpoint. Temperature moves the equilibrium constant only mildly, about 0.03 in pK₁ across the range from 20 °C to 30 °C, but it also affects the pH reading itself, so measure both at the same time and on the same sample.

All of it. A tank carries its own carbonate hardness, its own temperature, its own substrate and additive declarations, its own target range and its own saved readings. Switch tanks and the result, the verdict, the validity locks, the history chart and the export all follow the tank you switched to. A shrimp tank at 2 dKH and a high-tech scape at 6 dKH never share a number or a curve.

You switch from the tank menu at the top of the History tab, or from Settings → Tanks. Multiple tanks are part of CO2Scape Pro; the free app keeps one, and its readings are never locked away.

Open the app, go to Settings → Restore purchases, and make sure the device is signed in to the same Apple Account that made the purchase. The purchase is non-consumable, so a restore does not charge you again and may be repeated as often as needed.

If Family Sharing is enabled for your family group, family members can also access it through the App Store using their own Apple Account.

Refunds for App Store purchases are handled by Apple, not by me, and I receive no payment data at all. Use reportaproblem.apple.com and sign in with the Apple Account that made the purchase.

If something in the app misled you into buying, tell me anyway. I would rather fix the wording than have you spend a support ticket on it.

Five things: no advertising, an unlimited number of tank profiles instead of one, an unlimited history instead of the last 30 saved readings, reminders at your chosen interval while a pH session is running, and CSV export.

Everything else is in the free app and stays there: all three methods, the error band on every result, the validity locks and the routes they point to, the drop checker scale with the reference-fluid recipe, the tools for volume, hardness units and dosing, pH sessions with the curve and the drift reading, and one tank whose readings are saved and kept. The purchase extends the record-keeping side of the app, not the chemistry.

If a feature you paid for does not appear after the purchase, force-quit and relaunch the app once; if it still does not, write to me with your app version.

Nothing you enter leaves the device. There is no account, no login, no synchronisation and no analytics of mine, and every tank and reading is written to the app’s own storage on your iPhone.

Two things do use the network. Apple’s own App Store machinery delivers the app and handles the purchase of CO2Scape Pro. And the free version shows advertising, which Google’s ad kit loads over the network and which asks for your consent before it starts. CO2Scape Pro removes the advertising. You can change your advertising choices at any time under Settings, and the details are set out in the privacy policy.

On your device, in the app’s own storage. There is no account and no server of mine that holds a copy, which also means I cannot recover anything for you.

Press and hold an entry in the History tab to delete it. The same gesture on a tank in Settings removes that tank together with the readings belonging to it. To remove everything at once, delete the app from the device. Before you do any of that, consider exporting your log, because deletion is final. CSV export is part of CO2Scape Pro.

Through the standard iOS device transfer or an encrypted device backup, which includes the app’s data container. If you set the new device up as new instead, export your readings beforehand and keep the file. That export is part of CO2Scape Pro.